One goal of designers of combustors, such as those used in the gas turbine engines of high performance aircraft, to minimize the amount of smoke and other pollutants produced by the combustion process in the gas turbine engine. For military aircraft in particular, smoke production creates a "signature" which makes high flying aircraft much easier to spot than if no smoke trail is visible. Accordingly, designers seek to design combustors to minimize smoke production.
Another goal of designers of combustors for high performance aircraft is to maximize the "relight stability" of a combustor. The term "relight stability" refers to the ability to initiate the combustion process at high airflows and low pressures after some event has extinguished the combustion process. Poor relight stability can lead to loss of an aircraft and/or a loss of life, depending on the conditions at the time the combustor failed to relight. In the typical combustors in use in gas turbines today, relight stability is directly related to total airflow in the combustor.
As those skilled in the art will readily appreciate, smoke production can be minimized by leaning out the fuel/air mixture in the combustor. Likewise, relight stability can be increased by enriching the fuel/air mixture. Thus, in the past, designers of combustors have faced the problem of having to choose between low smoke production and high relight stability. This problem was addressed by the inventor of the present application and others in a paper entitled "Fuel Injector Characterization and Design Methodology to Improve Lean Stability" which was presented at a conference of the American Institute of Aeronautics and Astronautics in 1985.
What is needed is method and apparatus which reduces smoke production and increases relight stability in the combustor of a gas turbine engine.